Matched bolt/carrier set is machined to mil-spec dimensions using the latest manufacturing and quality-control techniques to deliver superb reliability in both semi-auto and select-fire rifles. Carrier is hard-chromed inside and has an M16-type full-length shroud on the underside to trip the auto sear on full-auto/burst rifles. Bolt is magnetic particle inspected to ensure there are no internal flaws to compromise structural integrity and cause premature failure. Fully staked carrier key and tool steel extractor further aid reliable cycling. Laser-engraved Spike’s Tactical logo on the side of the carrier is visible when the ejection port door is open. .223/5.56 fits standard AR-15/M16/M4 rifles and is available with standard MIL-STD-171 5.3.1.2 phosphate finish.